TemplateMethod

Template Method

One-line pattern summary

A pattern where the overall procedure is fixed, while only the detailed steps are changed in subclasses.

Typical Unity use cases

• When the skill execution order is the same but the effect differs.
• When common pre-processing and post-processing must be enforced.

Parts (roles)

• Template Method
• Primitive Operation
• Concrete Class

Unity example (C#)

The code below is a simplified Unity example based on the scenario described above.

public abstract class SkillExecutionTemplate
{
    public void Execute()
    {
        if (!CanExecute())
        {
            return;
        }

        ConsumeCost();
        PlayCastAnimation();
        ApplyEffect();
    }

    protected virtual bool CanExecute() => true;
    protected virtual void ConsumeCost() { }
    protected virtual void PlayCastAnimation() { }
    protected abstract void ApplyEffect();
}

public sealed class HealSkillTemplate : SkillExecutionTemplate
{
    protected override void ApplyEffect()
    {
        // Heal target.
    }
}

Advantages

• Behavior is separated into smaller units, which reduces the impact of changes.
• Adding or swapping rules is relatively safe.

Things to watch out for

• As the number of objects and indirect calls increases, the flow can become harder to follow.
• Ordering bugs should be pinned down with tests.

Interaction diagram

This shows the flow where the parent fixes the algorithm order and the subclass changes only some steps.